Fe₃C/Fe nanoparticles decorated three-dimensional nitrogen-doped carbon foams for highly efficient bisphenol A removal through peroxymonosulfate activation

The design of heterogeneous catalysts has become one of the most important steps in the popularization of advanced oxidation processes for wastewater remediation. With a nitrate-assisted polymer-bubbling strategy, we prepared three-dimensional carbon foams decorated by commensal Fe₃C/Fe nanoparticles through a direct pyrolysis of the mixture of polyvinyl pyrrolidone and ferric nitrate nonahydrate. The as-obtained composites, Fe₃C/Fe@NCFs, are employed as heterogeneous peroxymonosulfate (PMS) activators to remove bisphenol A (BPA) in aquatic environments with a predetermined concentration. It is found that both Fe₃C/Fe nanoparticles and N-doped carbon frameworks can activate PMS to release powerful oxidative species for BPA removal. The effect of pyrolysis temperature on the catalytic performance of Fe₃C/Fe@NCFs is studied in detail. The results reveal that high pyrolysis temperature induces the agglomeration of Fe₃C/Fe nanoparticles and the loss of N content, and low pyrolysis temperature only generates low-crystallinity carbon frameworks and small proportion of graphitic N configuration. Therefore, Fe₃C/Fe@NCFs from moderate temperature (700 °C) can produce the highest BPA removal efficiency. The synergy of Fe₃C/Fe nanoparticles and N-doped carbon frameworks, as well as the structure advantages is clearly established in comparison with some control samples. Quenching experiments and electron paramagnetic resonance (EPR) tests indicate that BPA can be degraded in both radical pathway and non-radical pathway, where SO₄^[rad]−, [rad]O₂⁻, and ¹O₂ are primary reactive species. In addition, the influences of some routine factors and actual water backgrounds were also investigated and analyzed comprehensively.